Inhibitory role of ERβ on anterior pituitary cell proliferation by controlling the expression of proteins related to cell cycle progression

Revealing Sexual Dimorphism in Prolactin Regulation From Early Postnatal Development to Adulthood in Murine Models

Serum prolactin (PRL) levels exhibit a gradual rise both in male and female rats from birth to adulthood, with females consistently displaying higher levels compared to age-matched males. This pattern has traditionally been attributed to the development and maturation of endocrine and neuroendocrine networks responsible for regulating PRL synthesis and secretion. However, the effect of dopamine (DA), which acts as an inhibitory factor on lactotroph function, also increases from birth to puberty, particularly in females. Nonetheless, the secretion of PRL remains higher in females compared to males. On the other hand, the observed sex differences in serum PRL levels during early postnatal development cannot be attributed to the influence of estradiol (E2). While serum E2 levels gradually increase after birth, only after 45 days of life do the disparities in E2 levels between females and males become evident. These observations collectively suggest that neither the maturation of hypothalamic DA regulation nor the rise in E2 levels can account for the progressive and sustained elevation in serum PRL levels and the observed sexual dimorphism during postnatal development. This review highlights the importance of recent discoveries in animal models that shed light on inhibitory mechanisms in the control of PRL secretion within the pituitary gland itself, that is intrapituitary mechanisms, with a specific emphasis on the role of transforming growth factor β1 and activins in PRL secretion.

An approach to uncover the relationship between 17b-estradiol and ESR1/ESR2 ratio in the regulation of canine corpus luteum

The canine corpus luteum (CL) is able to synthetise, activate and deactivate 17b-estradiol (E2) and also expresses nuclear estrogen receptors in a time-dependent manner during diestrus. Nevertheless, we are still missing a better comprehension of E2 functions in the canine CL, especially regarding the specific roles of estrogen receptor alpha (ERa) and ERb, encoded by ESR1 and 2, respectively. For that purpose, we analyzed transcriptomic data of canine non-pregnant CL collected on days 10, 20, 30, 40, 50 and 60 of diestrus and searched for differentially expressed genes (DEG) containing predicted transcription factor binding sites (TFBS) for ESR1 or ESR2. Based on biological functions of DEG presenting TFBS, expression of select transcripts and corresponding proteins was assessed. Additionally, luteal cells were collected across specific time points during diestrus and specificity of E2 responses was tested using ERa and/or ERb inhibitors. Bioinformatic analyses revealed 517 DEGs containing TFBS, from which 67 for both receptors. In general, abundance of predicted ESR1 targets was greater in the beginning, while abundance of ESR2 targets was greater in the end of diestrus. ESR1/ESR2 ratio shifted from an increasing to a decreasing pattern from day 30 to 40 post ovulation. Specific receptor inhibition suggested an ERa-mediated positive regulation of CL function at the beginning of diestrus and an ERb-mediated effect contributing to luteal regression. In conclusion, our data points toward a broad spectrum of action of E2 and its nuclear receptors, which can also act as transcription factors for other genes regulating canine CL function.

Perinatal DEHP exposure modulates pituitary estrogen receptor α and β expression altering lactotroph and somatotroph cell growth in prepuberal and adult male rats

Phthalates are synthetic chemicals widely used to make polyvinylchloride (PVC) soft and flexible. Of these, Di-(2-ethylhexyl) phthalate (DEHP) is the most commonly used, with high human exposure occurring as early as the fetal developmental stage and affecting the endocrine system. We focused on the perinatal DEHP effects on pituitary estrogen receptor (ER) expression in male rats, explored their impact on lactotroph and somatotroph cell growth, and evaluated the direct effects of this phthalate on pituitary cell cultures. Our results showed that DEHP perinatal exposure was unable to modify the ERα+ pituitary cell number from prepuberal rats, but increased ERβ+ cells. In adulthood, the pituitary ERα+ cells underwent a slight decrease with ERβ showing the greatest changes, and with a significant increase observed in somatotroph cells. Also, in vitro, DEHP reduced the ERα+ cells, increased the percentage of ERβ+ pituitary cells and modified the Ki67 index, as well as decreasing the lactotrophs and increasing the somatotroph cells. In conclusion, the present study showed that DEHP induced ER expression changes in normal pituitary glands from male rats in in vivo and in vitro conditions, suggesting that DEHP could differentially modulate lactotroph and somatotroph cell growth, possibly as a consequence of ER imbalance.

ET-1 regulates the human umbilical vein endothelial cell cycle by adjusting the ERβ/FOXN1 signaling pathway

Background

Atherosclerosis (AS) is a chronic and progressive disease primarily induced by inflammation of the arterial blood vessel wall. Investigating the function and molecular regulation mechanisms of ET-1, ERβ, and FOXN1 in disease models will provide new targets and means for clinical treatment.

Methods

The effects of ET-1 on oxidative stress in HUVEC were verified through quantitative polymerase chain reaction (qPCR), western blot, flow cytometry, as well as dual luciferase reporter gene and biochemical assays.

Results

Compared with the ET-1+ negative control (NC) group, the ERβ messenger ribonucleic acid (mRNA) expression level was significantly reduced, and the FOXN1 mRNA expression level increased markedly in the ET-1 + ERβ small interfering ribonucleic acid (siRNA) group. Meanwhile, the FOXN1 mRNA expression level was significantly reduced in the ET-1 + FOXN1 siRNA group. FOXN1 promoter luciferase reporter gene activity was notably enhanced in the ERβ siRNA group compared with the siRNA control group. Compared with the ET-1 + NC group, the levels of reaction oxygen species (ROS) in the ET-1 + ERβ siRNA group increased considerably, the superoxide dismutase (SOD) level was significantly reduced, and the G0/G1 phase cell ratio was reduced. In addition, the protein expression of ERβ and cyclin B1 (CCNB1) was markedly reduced, whereas the protein expression of cyclin A2 (CCNA2), cyclin D1 (CCND1), and cyclin E1 (CCNE1) increased substantially. The opposite result was observed in the ET-1 + FOXN1 siRNA group.

Conclusions

ET-1 can contribute to the expression of ERβ and FOXN1. ERβ can inhibit the expression of FOXN1 by regulating promoter activity. The ET-1/ERβ/FOXN1 signaling pathway is involved in the regulation of oxidative stress and cycle progression in HUVEC. This study provides a new mechanism for the regulation of umbilical vein endothelial cells. The ET-1/ERβ/FOXN1 signaling pathway may provide novel therapeutic targets and strategies for the treatment of atherosclerosis.

The phthalate DEHP modulates the estrogen receptors α and β increasing lactotroph cell population in female pituitary glands

Humans are exposed to numerous endocrine disruptors on a daily basis, which may interfere with endogenous estrogens, with Di-(2-ethylhexyl) phthalate (DEHP) being one of the most employed. The anterior pituitary gland is a target of 17β-estradiol (E2) through the specific estrogen receptors (ERs) α and β, whose expression levels fluctuate in the gland under different contexts, and the ERα/β index is responsible for the final E2 effect. The aim of the present study was to evaluate in vivo and in vitro the DEHP effects on ERα and β expression in the pituitary cell population, and also its impact on lactotroph and somatotroph cell growth. Our results revealed that perinatal exposure to DEHP altered the ERα and β expression pattern in pituitary glands from prepubertal and adult female rats and increased the percentage of lactotroph cells in adulthood. In the in vitro system, DEHP down-regulated ERα and β expression, and as a result increased the ERα/β ratio and decreased the percentages of lactotrophs and somatotrophs expressing ERα and β. In addition, DEHP increased the S + G2M phases, Ki67 index and cyclin D1 in vitro, leading to a rise in the lactotroph and somatotroph cell populations. These results showed that DEHP modified the pituitary ERα and β expression in lactotrophs and somatotrophs from female rats and had an impact on the pituitary cell growth. These changes in ER expression may be a mechanism underlying DEHP exposure in the pituitary gland, leading to cell growth deregulation.

Roles of estrogen receptor α and β in the regulation of proliferation in endometrial carcinoma

Endometrial carcinoma (EC), an estrogen-dependent gynecological malignancy, is prevalent worldwide. Estrogen receptor α (ERα) and estrogen receptor β (ERβ) are two main estrogen receptor isoforms, which mediate estrogen-induced proliferation in EC. However, the dynamic changes of ERα and ERβ subtype expression and their functions on proliferation in EC remain elusive. In this study, we aimed to investigate the expression of ERα and ERβ in para-tumor eutopic endometrium, endometrial atypical hyperplasia and EC by immunohistochemistry and then analyse their clinical significance. Subsequently, Ishikawa cells with ERα or ERβ knockdown by lentivirus transfection were used to explore the relationship between ERα/ERβ and cell proliferation, and preliminarily evaluate whether metformin's inhibitory effect on estrogen-induced cell proliferation was mediated by ERα and ERβ. We found that the expression of ERα and ERβ were markedly changed in endometrial hyperplasia and EC compared with that in para-tumor eutopic endometrium and exhibited different expression trends. Through further analysis, we discovered that ERα presented higher expression in endometrial atypical hyperplasia and early stage of EC than that in para-tumor eutopic endometrium, while the expression of ERβ gradually decreased from para-tumor eutopic endometrium to EC. Additionally, the cell cycle-related protein, CyclinD1 was gradually increased but p21 decreased. Furthermore, knockdown of ERα and ERβ severally in Ishikawa cells either inhibited or promoted estrogen-induced cell proliferation through regulating CyclinD1 and p21 expression. Meanwhile, the inhibitory effect of metformin on estrogen-induced cell proliferation was respectively blunted or partly reversed by knockdown of ERα or ERβ. Altogether, ERα and ERβ have different expression patterns in the progression of EC either facilitating or suppressing cell proliferation through regulating the expression of CyclinD1 and p21 in EC cells, and may also mediate the inhibitory effect of metformin on estrogen-induced EC cells proliferation.

mPRs represent a novel target for PRL inhibition in experimental prolactinomas

Membrane progesterone receptors are known to mediate rapid nongenomic progesterone effects in different cell types. Recent evidence revealed that mPRα is highly expressed in the rat pituitary, being primarily localized in lactotrophs, acting as an intermediary of P4-inhibitory actions on prolactin secretion. The role of mPRs in prolactinoma development remains unclear. We hypothesize that mPR agonists represent a novel tool for hyperprolactinemia treatment. To this end, pituitary expression of mPRs was studied in three animal models of prolactinoma. Expression of mPRs and nuclear receptor was significantly decreased in tumoral pituitaries compared to normal ones. However, the relative proportion of mPRα and mPRβ was highly increased in prolactinomas. Interestingly, the selective mPR agonist (Org OD 02-0) significantly inhibited PRL release in both normal and tumoral pituitary explants, displaying a more pronounced effect in tumoral tissues. As P4 also regulates PRL secretion indirectly, by acting on dopaminergic neurons, we studied mPR involvement in this effect. We found that the hypothalamus has a high expression of mPRs. Interestingly, both P4 and OrgOD 02-0 increased dopamine release in hypothalamus explants. Moreover, in an in vivo treatment, that allows both, pituitary and hypothalamus actions, the mPR agonist strongly reduced the hyperprolactinemia in transgenic females carrying prolactinoma. Finally, we also found and interesting gender difference: males express higher levels of pituitary mPRα/β, a sex that does not develop prolactinoma in these mice models. Taken together, these findings suggest mPRs activation could represent a novel tool for hyperprolactinemic patients, especially those that present resistance to dopaminergic drugs.

The ERα membrane pool modulates the proliferation of pituitary tumours

The molecular mechanisms underlying the ERα nuclear/cytoplasmic pool that modulates pituitary cell proliferation have been widely described, but it is still not clear how ERα is targeted to the plasma membrane. The aim of this study was to analyse ERα palmitoylation and the plasma membrane ERα (mERα) pool, and their participation in E2-triggered membrane-initiated signalling in normal and pituitary tumour cell growth. Cell cultures were prepared from anterior pituitaries of female Wistar rats and tumour GH3 cells, and treated with 10 nM of oestradiol (E2). The basal expression of ERα was higher in tumour GH3 than in normal pituitary cells. Full-length palmitoylated ERα was observed in normal and pituitary tumour cells, demonstrating that E2 stimulation increased both, ERα in plasma membrane and ERα and caveolin-1 interaction after short-term treatment. In addition, the Dhhc7 and Dhhc21 palmitoylases were negatively regulated after sustained stimulation of E2 for 3 h. Although the uptake of BrdU into the nucleus in normal pituitary cells was not modified by E2, a significant increase in the GH3 tumoural cell, as well as ERK1/2 activation, with this effect being mimicked by PPT, a selective antagonist of ERα. These proliferative effects were blocked by ICI 182780 and the global inhibitor of palmitoylation. These findings indicate that ERα palmitoylation modulated the mERα pool and consequently the ERK1/2 pathway, thereby contributing to pituitary tumour cell proliferation. These results suggest that the plasma membrane ERα pool might be related to the proliferative behaviour of prolactinoma and may be a marker of pituitary tumour growth.

Role of GPER in the anterior pituitary gland focusing on lactotroph function

Ovarian steroids control a variety of physiological functions. They exert actions through classical nuclear steroid receptors, but rapid non-genomic actions through specific membrane steroid receptors have been also described. In this study, we demonstrate that the G-protein-coupled estrogen receptor (GPER) is expressed in the rat pituitary gland and, at a high level, in the lactotroph population. Our results revealed that ~40% of the anterior pituitary cells are GPER positive and ~35% of the lactotrophs are GPER positive. By immunocytochemical and immuno-electron-microscopy studies, we demonstrated that GPER is localized in the plasmatic membrane but is also associated to the endoplasmic reticulum in rat lactotrophs. Moreover, we found that local Gper expression is regulated negatively by 17β-estradiol (E2) and progesterone (P4) and fluctuates during the estrus cycle, being minimal in proestrus. Interestingly, lack of ovarian steroids after an ovariectomy (OVX) significantly increased pituitary GPER expression specifically in the three morphologically different subtypes of lactotrophs. We found a rapid estradiol stimulatory effect on PRL secretion mediated by GPER, both in vitro and ex vivo, using a GPER agonist G1, and this effect was prevented by the GPER antagonist G36, demonstrating a novel role for this receptor. Then, the increased pituitary GPER expression after OVX could lead to alterations in the pituitary function as all three lactotroph subtypes are target of GPER ligand and could be involved in the PRL secretion mediated by GPER. Therefore, it should be taken into consideration in the response of the gland to an eventual hormone replacement therapy.

Estrogen receptor β regulates the tumoral suppressor PTEN to modulate pituitary cell growth

In this study, we focused on ERβ regulation in the adenohypophysis under different estrogenic milieu, by analyzing whether ER modulates the phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expression and its subcellular localization on anterior pituitary glands from Wistar rats and GH3 lactosomatotroph cells that over-expressed ERβ. ERβ was regulated in a cyclic manner, and underwent dynamic changes throughout the estrous cycle, with decreased ERβ+ cells in estrus and under E2 treatment, but increased in ovariectomized rats. In addition, the ERα/β ratio increased in estrus and under E2 stimulation, but decreased in ovariectomized rats. Double immunofluorescence revealed that lactotroph and somatotroph ERβ+ were significantly decreased in estrus. Also, variations in the PTEN expression was observed, which was diminished with high E2 conditions but augmented with low E2 milieu. The subcellular localization of this phosphatase was cell cycle-dependent, with remarkable changes in the immunostaining pattern: nuclear in arrested pituitary cells but cytoplasmic in stimulated cells, and responding differently to ER agonists, with only DPN being able to increase PTEN expression and retaining it in the nucleus. Finally, ERβ over-expression increased PTEN with a noticeable subcellular redistribution, and with a significant nuclear signal increase in correlation with an increase of cells in G0/G1 phase. These results showed that E2 is able to inhibit ERβ expression and suggests that the tumoral suppressor PTEN might be one of the signaling proteins by which E2, through ERβ, acts to modulate pituitary cell proliferation, thereby adapting endocrine populations in relation with hormonal necessities.

Berberine promotes proliferation of sodium nitroprusside-stimulated rat chondrocytes and osteoarthritic rat cartilage via Wnt/β-catenin pathway

Berberine chloride (BBR) is an isoquinoline derivative alkaloid isolated from medicinal herbs, including Coptis chinensis and Berberis aristate. This compound plays significant roles in the treatment of osteoarthritis (OA). The purpose of this study was to investigate the effects of BBR on the proliferation of sodium nitroprusside (SNP)-stimulated chondrocytes in vitro, the articular cartilage in a rat OA model, as well as to discuss the molecular mechanisms underlying these effects. In vitro, we demonstrated that BBR led to cell proliferation, increased the cell population in S-phase and decreased that in G0/G1-phase; moreover, the F-actin remodeling in SNP-stimulated chondrocytes were prevented. In addition, BBR markedly up-regulated β-catenin, c-Myc, and cyclin D1 expression of genes and proteins, and down-regulated glycogen synthase kinase-3β (GSK-3β) and matrix metalloproteinase-7 (MMP-7) expression. Notably, inhibition of the Wnt/β-catenin pathway by XAV939 partially blocked these effects. The in vivo results suggested that BBR promoted β-catenin protein level and enhanced proliferating cell nuclear antigen (PCNA) expression in osteoarthritic rat cartilage. In conclusion, these findings indicate that BBR promotes SNP-stimulated chondrocyte proliferation by promoting G1/S phase transition and synthesis of PCNA in cartilage through activation of Wnt/β-catenin signaling pathway.